The New York-based human rights group said in its report that the two month-long violence included the use of arbitrary and disproportionate force by the administration.
Nepal's new government should immediately investigate alleged use of arbitrary force by police and extrajudicial killings during ongoing protests over the country's new Constitution by ethnic groups which were led by Indian-origin Madhesis, Human Rights Watch said today.
"Nepali authorities should immediately investigate and bring to justice those responsible for killings and other violations during ongoing protests over the constitutional debate," Human Rights Watch (HRW) said in a new report that claimed at least 45 people were killed during the protests.
The New York-based human rights group said in its 44-page report that the two month-long violence included the use of arbitrary and disproportionate force, and extrajudicial killings by the police against protesters; killing of children; and murders of police officers as well.
The agitation launched by Indian-origin Madhesis, who are protesting division of their ancestral homeland in the new Constitution, and Tharu ethnic groups in southern plains have continued since August in the southern plains and escalated to blockading of a key border trade point with India.
"While the drafting of a rights-respecting Constitution is an emotional issue in Nepal, disagreements cannot be resolved by committing serious human rights abuses," said Brad Adams, Asia director.
"The government has the responsibility to ensure there are impartial and effective investigations and cannot simply look the other way," he said.
The report titled 'Like We Are Not Nepali: Protest and Police Crackdown in the Terai Region of Nepal' documents HRW investigations into the killings of 25 people, including 16 members of the public and 9 police officers, in five Terai districts between August 24 and September 11, 2015.
The rights body said it found no evidence that any of these victims were posing a threat at the time that they were killed.
"Nepal's new leadership should take immediate steps to stem the tide of abuse that has overtaken Nepal the last few months... The government needs to order investigations, and publicly call on all security forces to desist from any excessive use of force," said Mr Adams.